Due to rise in combustion temperature posed by high efficiency of a gas turbine, a material of rotor blades and stator blades of turbines has varied from the conventionally cast alloy to a directionally solidified alloy in which crystal grain boundary in a stress axis direction was eliminated to improve creep strength at high temperature, and further to a single crystal alloy in which the crystal grain boundary itself was eliminated. Furthermore, the single crystal alloy seeks further improvement of creep strength, and development of from the first generation single crystal alloy to the second generation and third generation single crystal alloys has proceeded. The first generation single crystal alloy is an alloy to which rhenium (Re) is not added, and examples thereof include CMSX-2 (Patent Document 1), Rene' N4 (Patent Document 2) and PWA-1480 (patent Document 3).
The second generation single crystal alloy is an alloy in which creep resistant temperature was improved about 30° C. than the first generation single crystal alloy by adding about 3% of rhenium, and examples thereof include CMSX-4 (Patent Document 4), PWA-1484 (Patent Document 5) and Rene' N5 (Patent Document 6).
The third generation single crystal alloy is an alloy in which creep resistant temperature was tried to improve by adding 5-6% of rhenium, and example thereof is CMSX-10 (Patent Document 7). The above single crystal superalloy has remarkably developed as a blade material of jet engines for mainly aircrafts. Due to demand of high temperature for the purpose of improving combustion efficiency, technical transfer is attempted to industrial large-sized gas turbines.    Patent Document 1: JP-A-59-19032    Patent Document 2: U.S. Pat. No. 5,399,313    Patent Document 3: JP-A-53-146223    Patent Document 4: U.S. Pat. No. 4,643,782    Patent Document 5: U.S. Pat. No. 4,719,080    Patent Document 6: JP-A-5-59474    Patent Document 7: JP-A-7-138683